This invention relates to methods of reducing or scavenging the amount of hydrogen sulfide in a hydrogen or sulfide-containing aqueous or wet gaseous mediums.
The reactivity between various aldehydes and sulfidic compounds (H.sub.2 S, mercaptans, etc.) has been known in the art for sometime. For example, Marks in U.S. Pat. No. 1,991,765 discloses a method of reacting hydrogen sulfide and an aldehyde in an aqueous solution having a pH between 2 and 12 at a temperature between substantially 20.degree. C. and 100.degree. C. After Marks' disclosure in 1935, many patents appeared disclosing the use of aldehydes during acid cleaning of iron sulfide deposits, including U.S. Pat. Nos. 2,606,873; 3,514,410; 3,585,069; 3,669,613; 4,220,550; 4,289,639; and 4,310,435. Consumption of the hydrogen sulfide liberated by acidification of sulfide-containing deposits increased the safety of such operations. Decreased corrosivity of the aldehyde-containing acids is also disclosed in the prior art, sometimes with the addition of ancillary corrosion inhibitors.
Menaul in U.S. Pat. No. 2,426,318 discloses a method of inhibiting the corrosive action of natural gas and oil containing soluble sulfides on metals by utilizing an aldehyde and preferably formaldehyde.
Roehm in U.S. Pat. No. 3,459,852 discloses a process for deodorizing and reducing the biochemical demand of an aqueous solution which contains at least one compound of hydrogen sulfide and compounds containing the --SH group. Roehm's process comprises mixing the solution with a sulfide-active alpha, beta unsaturated aldehyde or ketone in an amount sufficient to form sulfur-containing reaction product of the sulfide active aldehyde or ketone. More specifically, Roehm's invention resides in the use of compounds having the following alpha, beta unsaturated aldehyde or ketone moiety as the reactive portion: ##STR1## Two such sulfide-active compounds disclosed by Roehm are acrolein and 3-buten-2-one.
Formaldehye, formaldehyde with SO.sub.3.sup.-2, and acrolein are all commercially used hydrogen sulfide (H.sub.2 S) scavengers. However, formaldehyde produces a solid reaction product and reverts readily to formaldehyde and free H.sub.2 S. Acrolein is more expensive than formaldehyde as well as extremely toxic and dangerous to handle. The use of SO.sub.3.sup.-2 with formaldehyde eliminates the re-release of H.sub.2 S but not solids formation.
Despite the prior art approaches to H.sub.2 S scavenging, the provision of a single compound or group of compounds capable of providing the H.sub.2 S scavenging funcion while not producing a solid reaction product and without stringent handling problems is highly desirable from a commercial point of view. Such a compound or compounds would provide suitable H.sub.2 S scavengers for systems where solids must be avoided. These needs are effectively met by utilization of the hydrogen sulfide scavenging methods of the present invention.